Models were developed using human bronchial epithelial (HBE) cells for studying compounds reputed to be cocarcinogens and/or tumor promoters in animal models. Compounds were tested for cytotoxicity by colony forming efficiency (CFE) and population doubling time (PDT) assays. The compounds were then screened using concentrations that were maximally mitogenic or that gave no more than 50% cell death by observing effects on cells exposed for 6 hrs. They were observed for morphologic changes under light microscopy and assayed for change in ornithine decarboxylase (ODC), plasminogen activator (PA), aryl hydrocarbon hydroxylase (AHH) activity, and cross-linked envelope (CLE) formation. Initial findings indicate that 12-0-tetradecanoylphorbol-13-acetate (TPA) or teleocidin (1-100 nM) induce differentiation which is accompanied by an increase in PA and CLE formation while other compounds tested thus far cause some mitogenicity with increased AHH formation or no observable effect. When these initial studies are completed, selected compounds will be used for in vitro carcinogenesis experiments and to investigate their mechanisms of action.